However, in recent years several hundred have washed ashore suffering the effects of a hypothermic reaction to dropping water temperatures - suffering decreased heart rate and lethargy, followed by shock, pneumonia and sometimes death.

Temperatures warmed a degree or two in the following days and, with a shift in wind direction, more turtles have been found alive, he added.

In all, at least 219 have been recovered during the past three days,

They are brought north by the Gulf Stream and spend their summers eating shrimp and shellfish, before returning south as temperatures drop.

No-one is quite sure why some are left behind. Researchers speculate that global warming is encouraging them to linger, making them vulnerable to sudden cold snaps.

“It is thought that animals foraging in shallow bays and inlets become susceptible to cold stunning because the temperatures in these areas can drop quite rapidly and unexpectedly,” says the National Oceanic and Atmospheric Administration.

“Recently, we've been averaging about 600 cold-stunned sea turtles in Massachusetts from late October through December. In addition, New York, specifically Long Island beaches, also see several cold stunned turtles each winter.”

It says that loggerhead sea turtles and green sea turtles are also affected.